Use of energy reserves in fighting hermit crabs

Abstract

When animals engage in fights they face a series of decisions, which are based on the value of the contested resource and either their relative or their absolute fighting ability. Certain correlates of fighting ability or 'resource holding potential' such as body size are fixed but physiological correlates are expected to vary during the encounter. We examine the role of energy reserves in determining fight outcomes and parameters during 'shell fighting' in hermit crabs. During these fights, the two contestants perform very different roles of attacker and defender. We show that the balance of the total energy pool, in the form of glucose and glycogen, determines the ability of defenders to resist eviction from their shells. Low glucose in evicted defenders is not caused by depletion of energy reserves, rather mobilization of glycogen appears to be the result of a strategic decision about whether to resist effectively, based on the perceived fighting ability of the attacker. Attackers, however, always initiate the fight so such a decision for this role appears unlikely. In addition to influencing decisions and ability during fights, physiological correlates of fighting ability can in turn be influenced by strategic decisions.

Lactate accumulation in the intertidal hermit crab, <i>Pagurus samuelis</i>, in response to burial-induced hypoxia

“…Instead, we suggest a different cause of death. Hermit crabs have two internal sources of energy, circulating glucose and stored glycogen (Briffa & Elwood, 2004). Once circulating glucose has been utilized, glycogen stored in muscles and hepatopancreas is likely the most rapidly accessible and most helpful glycogen source during severe acute demands for energy.…”

“…In order for hermit crabs to employ glycolysis and lactic acid fermentation they must have a supply of glucose. Previous work indicates that, in decapods, glycogen serves as the glucose source once hemolymph glucose has been depleted (Briffa & Elwood, 2004;Hill et al, 1991;Sneddon et al, 1999). Although aerobic respiration yields significantly more ATP molecules, anaerobiosis may be utilized in P. samuelis to survive acute and relatively short-term environmental hypoxia.…”

Shell occupation by the South Atlantic endemic hermit crab Loxopagurus loxochelis (Moreira, 1901) (Anomura: Diogenidae)

“…According to Abrams (1988), females deviate part of the energy for gonad development, while males invest in growth to ensure copulation when there are other males vying for the same female. The growth spends a greater cost of energy and time, since to grow they need, besides the usual metabolic processes, to constantly change their shells (Hazlett, 1981;Briffa and Elwood, 2004;Gherardi, 2006).…”

The role of skill in animal contests: a neglected component of fighting ability

“…Strength is an example of a performance capacity and overall stamina has also been revealed as an important performance capacity that can increase the chances of victory [23]. Stamina in turn is dependent on energy reserves, aerobic capacity [24] and metabolic rate [25]. Thus, morphological and physiological traits seem fundamentally important to the outcome of animal fights.…”